FR2632414A1 - FERROMAGNETIC MEASURING APPARATUS - Google Patents

Abstract

Ferromagnetic measuring device comprising, a coil 1 provided with a hollow barrel 2 and on which is produced a winding of a conductive wire, a mobile unit 5 integral with a needle 7 moving in front of a dial graduated between a zero value and a maximum value, this moving unit being integral with a first metal pallet 19 moving, during the measurement of an electrical quantity, relative to a second metal pallet fixed in the hollow barrel of the coil, as a function of the magnetic field created by the winding, apparatus characterized in that it comprises a third metal pallet 21, 22 fixed in the hollow barrel of the coil, so as to cooperate with the movable pallet 19 to brake the pivoting of the movable assembly when the electrical quantity to be measured tends to move the needle 7 of the mobile unit beyond the maximum value of the graduation.

Description

26324 1 4

  The invention relates to a ferromagnetic measuring device. There are already known so-called "motor scale" measuring devices whose graduated dial, in front of which the indicator hand moves, extends beyond the maximum value of the graduation by a

  area not graduated but which can be reached by means of it

  guille when the device is traversed by -a surin-

  transient density such as that which appears during

starting an engine.

  This arrangement makes it possible to postpone the mechanical stop of the needle beyond this so-called motor scale zone of the dial, in order to prevent or

  at the very least to reduce the violence of the shock of the

  guille against this mechanical limit stop

during a fleeting overcurrent.

  The object of the present invention is to provide improvements to these devices and relates to

  this effect a ferromagnetic measuring device com-

  bearing, a coil provided with a hollow barrel and on

  which is carried out a winding of a conductive wire

  tor, a mobile assembly, integral with a needle moving in front of a dial graduated between a zero value and a maximum value, this movable assembly being integral with a first metal pallet

  moving, when measuring an electrical quantity

  that, with respect to a second metal pallet fixed in the hollow barrel of the coil, as a function of the magnetic field created by the winding, apparatus characterized in that it comprises a third metal pallet fixed in the hollow barrel of the coil, so as to cooperate with the movable pallet to brake the pivoting of the movable element when the electrical quantity to be measured tends to move the needle of the movable element beyond the maximum value of the graduation.

  According to another characteristic of the

  vention, the third blade is attached to the wall

internal of the hollow barrel.

  The invention is shown by way of example

  ple nonlimiting on the attached drawings in which:

  - Figure 1 is a schematic sectional view

  that axial of an embodiment of the measuring device according to the invention, - Figure 2 is a top view of Figure 1, the racket resetting the device being removed and the crew mobile being shown in dotted lines. The ferromagnetic device shown in the accompanying drawings comprises a coil 1, the hollow shaft 2 is made in one piece by molding a plastic material, with the upper flange 3, the lower flange 4 being snapped into 4. to the

base of barrel 2.

  The moving assembly 5 comprises a solid axis 6

  of the indicator needle 7, this movable assembly being, in the example shown, pivotally mounted along the axis XX, on the one hand by means of end pivot pins 7 and 8, on the other hand by knives 9 and 10 arranged in alignment with

these pivot points 7 and 8.

  The pivot point 7 cooperates for this purpose with a conical bearing 71 formed in a racket 11 pivotally mounted by a bayonet assembly 11, at the end of the barrel 2 of the coil 1. This racket 11 is connected to the end outside of the spiral return spring 12, the central end of which is immobilized on the axis 6 of the moving assembly. This arrangement allows, by the angular adjustment of the position of the racket 11, to reset the needle 7 on the graduated dial shown diagrammatically.

in 13 of the apparatus.

  The pivot point 8 cooperates with a conical bearing 8, formed in the bottom 14 of the hollow shaft 2. The knives 9 and 10 each cooperate with dihedrons 15 formed at the end of the two branches

  16. of a stirrup 16 whose base 162 forms approximately

a quarter of a circle.

  This bracket 16 is removably mounted inside the hollow barrel 2, by axial sliding

  between two ribs 17 and 18 projecting internally

laughing at the hollow barrel.

  The moving element 5 also includes a metal pallet 19 fixed to the axis 6 so as to be located radially inside the hollow barrel 2. By

  elsewhere, this hollow barrel 2 also comprises a pallet-

  metallic te 20 fixed radially projecting inside the barrel in a position such that when the winding of the conductive wire formed on the coil 1 is traversed by a current, the magnetic field created generates between the metallic pallets 19 and 20 a force repulsion tending to rotate the needle 7 in front of the graduation 13 by an angle depending on the value of the electrical quantity to be measured. According to the invention, this apparatus for

  ferromagnetic measurement also includes a third

  me metal pallet intended to constitute a stop

  magnetic designed to brake and limit movement

  of the needle beyond the maximum value 13, of the graduation 13 in order to thus surely avoid any deterioration of the measuring device when

undergoes a fleeting overcurrent.

  In the example shown, this third metal pallet is constituted by a double pallet 21 and 22 placed tangentially to the internal face of the barrel between the base 162 of the stirrup 16 and

this internal face of the barrel.

  When the needle 7 exceeds the maximum value

  mum 13, of the graduation 13, the force of repulsion existing between the pallet 19 and the pallets 21 and 22

  tends to brake and then prevent the pivoting of the

  guille 7, this force of repulsion being all the more important as the deflection of the needle 7 beyond

  the maximum graduation 13 is important.

  Of course, the position and dimensions of the metal pallets as well as the position of the graduations 13 of the dial, will be determined so as to take account of the combination of the different

  repulsion forces as a function of the angle of deviation

  tion of the needle, it being understood that, beyond the maximum graduation 131 the repulsion force generated by the pallets 21 and 22 on the pallet 19 becomes extremely preponderant compared to the action of

  repulsion exerted by the pallet 20.

  It will also be noted that in the example shown, the third fixed metal pallet is composed of two pallets 21 and 22. However, depending on the values of the quantities measured, as well as according to the sector covered by the graduation 13, this device may comprise a single pallet 21 or 22 arranged

  in either of the corresponding accommodation

  seen in the external face of the base 161 of the stirrup 16.

Claims (4)

  1) Ferromagnetic measuring device   bearing, a coil (1) provided with a hollow barrel (2) and   on which is carried a winding of a wire   ductor, a mobile assembly (5) integral with a needle (7) moving in front of a graduated dial '(13)   between a zero value and a maximum value, this equi-   mobile page being integral with a first metal pallet (19) moving, when measuring a   electrical quantity, compared to a second puck   metal te (20) fixed in the hollow barrel of the coil   depending on the magnetic field created by the winding   Lement, apparatus characterized in that it comprises a third metal pallet (21, 22) fixed in the hollow barrel of the coil, so as to cooperate with the movable pallet (19) to brake the pivoting of the movable assembly when the electrical quantity to be measured tends to move the needle (7) of the crew   moving beyond the maximum value (131) of the gra- duation.   2) Measuring device in accordance with the claim   cation 1, characterized in that the third pallet (21, 22) is fixed to the internal wall of the hollow barrel (2).   3) Measuring device conforming to one   conch of the preceding claims, characterized in   that the third pallet (19, 20) is fixed tangent   directly against the internal wall of the hollow barrel.   4) Measuring device conforming to one   conch of the preceding claims, characterized in   that the hollow barrel has several housings to receive, in one and / or the other of these housings, the third fixed pallet (19, 20).   ) Measuring device according to any one   conch of the preceding claims, characterized in   that the mobile assembly is pivotally mounted, on the one hand, by pivoting spikes (7, 8) and corresponding spans (71, 81), on the other hand by knives (9, 10) and corresponding bearing surfaces (15, 16), the knives or their bearing being formed on a stirrup (16) housed in the barrel (2), the third metal pallet (19, 20) being held in the barrel between   its internal face and the base (162) of the stirrup.